This proposal focuses on the fundamental issue of how people control the speech mechanism. It is first concerned with the discovery and cross-linguistic comparison of a set of time-varying articulatory parameters for vowels that can be used for specifying all the vacalic gestures that have been observed in the languages of the world. Then the principles underlying the dynamic control of these parameters will be addressed, starting with the production of diphthongs in several languages, because they constitute an important test case for studies on timing in speech. The ultimate aim is a model of articulatory speech control mechanisms, where it is possible to specify a set of control signals that will produce the correct variation in the underlying parameters, which would in turn generate the observed articulatory gestures. Studies will investigate the degrees of freedom involved in moving the tongue, the jaw, and the lips. We will formulate constraints on the spatio-temporal articulatory patterns of the tongue, the jaw, and the lips, and describe how these patterns differ between languages, between speakers, and between repetitions of words spoken by one individual. These studies will lead to further studies on compensatory articulation, investigating the extent to which equivalent vocal tract gestures can be produced by different articulators. Because our work is cross-linguistic, we will also be able to help quantify and elucidate the meaning of the useful but will defined notion of "base of articulation". The proposed studies will make a significant contribution to methodological questions involving the use of x-ray microbeam data and other movement data. Algorithms will be devised for comparing articulatory data from different individuals. A wide variety of languages will be used, leading to a better understanding of variation in natural languages and normal speech production, thus elucidating the problems of control in speech disorders.